AFP - Skirmishes broke out for a sixth day in central Athens Thursday after two police officers were charged over the killing of a teenager that sparked the rioting.

Around 40 youths threw stones at riot police near the university in Exarchia district where 15-year-old Andreas Grigoropoulos was shot dead on Saturday. They were met with volleys of teargas and three arrests were made, police said.

Greece fell deeper into turmoil on Wednesday, with a general strike adding to the government's woes.

Despite a vow by Prime Minister Costas Karamanlis to restore order, demonstrators battled security forces outside the Greek parliament as the nationwide stoppage halted flights in and out of Greece and closed banks, schools and some hospital services.

About 100 officers in riot gear defended the legislature against thousands of demonstrators. Turning their sights on the right-wing government, the protesters shouted: "Sack Karamanlis."

Petrol bombs were hurled as Alexis Kouyias, a lawyer for the police officers involved in the fatal shooting, was preparing to talk to reporters. Police said the youths responsible were friends of the dead boy.

Epaminondas Korkoneas, 37, was charged with voluntary homicide and "illegal use" of his service weapon. He was ordered to remain in custody by an Athens magistrate.

His partner, Vassilios Saraliotis, 31, was charged with being an accomplice and will also remain in custody. The pair have been held since Sunday.

According to the charge sheet, Korkoneas is alleged to have killed Grigoropoulos on Saturday during a clash with around 30 youths in Exarchia.

Under questioning by a magistrate, Korkoneas indicated he had acted out of self defence when the group began throwing firebombs and other objects while shouting that they "were going to kill them."

Legal sources have said the initial ballistics results indicate the bullet that killed Grigoropoulos did not hit the boy directly but ricocheted off a hard surface.

According to forensic scientists and independent experts acting for the Grigoropoulos family, the bullet "is a bit deformed, which showed the bullet touched a hard surface" before entering the boy's chest.

Elsewhere in the capital on Wednesday, demonstrators hurled fire bombs, pavement slabs, tangerines, water bottles and other missiles in rioting that continued at key flashpoints after nightfall.

A youth claimed to have been struck by a police officer and was taken to hospital along with a woman also hurt during clashes outside the Greek parliament, according to national health officials.

Similar troubles were reported in the northern city of Salonika where more than 80 shops and 14 banks were damaged, with ongoing occupation of university flashpoints.

A fresh student demonstration was scheduled for Thursday evening in Athens, the interior ministry said.

Outside Greece, about a dozen Turkish left-wing protestors daubed red paint over the front of the consulate in Istanbul, while the Greek embassies in Moscow and Rome were also targets for firebombers.

In Spain, 11 demonstrators were arrested and several police officers injured when clashes took place in Madrid and Barcelona, while 32 people were arrested in Copenhagen when their protest in support of Greek rioters turned violent, police said.

Anger at the police has been compounded by growing public frustration with the Karamanlis government over its economic policies and a string of recent scandals.

Airlines cancelled dozens of flights, while Greece's two biggest unions called for "the democratisation of the police and an end to violent and arbitrary acts by state organs."

The Athens Chamber of Commerce and Industry said 435 businesses had been hit, with 37 completely gutted.

In a televised address, Karamanlis pledged up to 10,000 euros (13,100 dollars) to stricken businesses, plus a tax freeze and government-guaranteed loans to rebuild burnt property.

Despite the turmoil, Karamanlis's office said he would attend a European Union summit in Brussels that starts Thursday.